Implement WebContentsViewChildFrame::TakeFocus.

third_party/WebKit/Source/core/page/FocusController.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nuanti Ltd.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 837 matching lines @@
 
 void FocusController::setFocused(bool focused) {
   if (isFocused() == focused)
     return;
 
   m_isFocused = focused;
 
   if (!m_isFocused && focusedOrMainFrame()->isLocalFrame())
     toLocalFrame(focusedOrMainFrame())->eventHandler().stopAutoscroll();
 
-  if (!m_focusedFrame)
+  // Do not set a focused frame when being unfocused. This might reset
+  // m_isFocused to true.
+  if (!m_focusedFrame && m_isFocused)

[dcheng, 2017/01/12 10:19:21]

This seems like a reasonable change to me, but I'm wondering if it's web visible
at all?

[avallee, 2017/01/12 20:00:23]

See the conversation here:
https://codereview.chromium.org/2474323002/diff/60001/third_party/WebKit/Sour...

[dcheng, 2017/01/20 07:02:38]

Would it be better to just pass false for notifyEmbedder here? After reading
this code, I haven't managed to convince myself this is OK. One of the places
that calls this function is WebViewImpl::setFocus(), and there's a fair amount
of work that's performed if there's a focused frame.

How do we end up here without any focused frames at all anyway?

[avallee, 2017/01/20 14:19:11]

Oh, i thought I had previously linked to the spot that clears the frame. If you
look here:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/page/Focu...

In the oopif case, we would hit the previous if block to advance focus out to
the embedder frame:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/page/Focu...

In the webview case, the page thinks it exists by itself, it's a main frame and
has reached the end of the content. In this case it returns focus to the
"Chrome" layer (just a different embedder).

     setFocusedFrame(m_page->mainFrame());
 
   // setFocusedFrame above might reject to update m_focusedFrame, or
   // m_focusedFrame might be changed by blur/focus event handlers.
   if (m_focusedFrame && m_focusedFrame->isLocalFrame() &&
       toLocalFrame(m_focusedFrame.get())->view()) {
     toLocalFrame(m_focusedFrame.get())->selection().setFocused(focused);
     dispatchEventsOnWindowAndFocusedElement(
         toLocalFrame(m_focusedFrame.get())->document(), focused);
   }
@@ skipping 524 matching lines @@
 
   return consumed;
 }
 
 DEFINE_TRACE(FocusController) {
   visitor->trace(m_page);
   visitor->trace(m_focusedFrame);
 }
 
 }  // namespace blink